1. Field of the Invention
The present invention relates to a control device for starting a fuel cell vehicle, and in particular, relates to a technique for starting the fuel cell in a hybrid-type power source device provided with a power storage unit for assisting a power supply from the fuel cell.
2. Description of the Related Art
Conventionally, a hybrid-type fuel cell power generation system is known, which comprises a fuel cell and a power storage unit such as a battery or a capacitor (electric double layer capacitor or condenser) in order to compensate the output responsiveness of the fuel cell, which is driven by a fuel gas supply. The fuel cell vehicle is installed with a solid polymer-type fuel cell, which is composed of a plurality of cells, each of which is formed by sandwiching a solid polymer electrolyte membrane corresponding to a solid polymer ion exchange membrane between an anode and a cathode.
In the above conventional hybrid-type fuel cell power generation system, when starting the fuel cell, first, air is supplied to a pressure control valve at the fuel side, for example, and fuel gas is supplied to the fuel electrode in response to air pressure supplied to the pressure control valve.
Thus, before starting the fuel cell, the power storage unit supplies electric driving power to the compressor which supplies air. In addition to auxiliary devices for driving the fuel cell, the power storage unit supplies electric power to the motor for driving the vehicle when the vehicle starts immediately after the start of the fuel cell, so that the power stored in the power storage unit is reduced, and the voltage between both terminals of the power storage unit is reduced.
When the fuel cell is connected to the power storage unit, whose voltage between both terminals has been reduced, a large current rapidly flows from the fuel cell to the power storage unit. In the course of translating the voltage between both terminals of the fuel cell and the power storage unit into a balanced state, the voltage between both terminals of the fuel cell is reduced. Then, the fuel cell is in danger of losing hydrogen or the water content in the solid polymer electrolyte film, or of experiencing a decrease in the durability of the fuel cell.
As described above, if the fuel cell is connected to the capacitor under a condition that the terminal voltage of the capacitor greatly differs from the terminal voltage of the fuel cell (output voltage of the fuel cell) at the time, for example, of starting the fuel cell, a large current may flow, which may cause a danger that the performance or the durability of the fuel cell will become deteriorated.